1. Field of the Invention
The present invention relates to a heteropolyacid catalyst including at least molybdenum (Mo), phosphorus (P), vanadium (V), and a first component selected from the group consisting of bismuth (Bi), boron (B) and mixtures or combinations thereof used in producing methacrylic acid by the gas-phase catalytic oxidation of an aldehyde or a mixture of aldehydes, and methods for making and using same.
More particularly, the present invention relates to a heteropolyacid catalyst including molybdenum (Mo), phosphorus (P), vanadium (V), and a first component selected from the group consisting of bismuth (Bi), boron (B) and mixtures or combinations thereof, where the catalyst is adapted to produce methacrylic acid by the gas-phase catalytic oxidation of an aldehyde feedstock including isobutanal (isobutyraldehyde) or isobutanal and methacrolein mixtures. The catalyst can also include copper (Cu). The catalyst can also include a second component selected from the group consisting of potassium (K), rubidium (Rb), cesium (Cs), thallium (Tl), and mixtures or combinations thereof. The catalyst can also include a third component selected from the group consisting of antimony (Sb), cerium (Ce), niobium (Nb), indium (In), iron (Fe), chromium (Cr), cobalt (Co), nickel (Ni), manganese (Mn), arsenic (As), silver (Ag), zinc (Zn), germanium (Ge), gallium (Ga), zirconium (Zr), magnesium (Mg), barium (Ba), lead (Pb), tin (Sn), titanium (Ti), aluminum (Al), silicon (Si), tantalum (Ta), tungsten (W), lanthanum (La), and mixtures or combinations thereof. The invention also relates to methods for making and using same.
2. Description of the Related Art
Isobutanal (isobutyraldehyde) is an intermediate of a process for production of methacrylic acid from propylene. Isobutyraldehyde is formed from the reaction of propylene, carbon monoxide and hydrogen, then oxidation of isobutyraldehyde produces methacrylic acid.
Isobutyraldehyde is also a by-product of 2-ethyl-hexanol production. In this process, propylene is hydroformylated to a mixture of n-butanal (n-butyraldehdye) and isobutanal (isobutyraldehyde). N-butanal is then converted to 2-ethyl-hexanol via base catalyzed oxidation and hydrogenation. Isobutanal is left as a by-product.
Nippon Shokubai has several patents on isobutyraldehyde oxidation. In U.S. Pat. No. 4,558,028, a catalyst for the oxidation of isobutyraldehyde was disclosed having a formula Mo12P1.09V1.09Cs1.0. In EP1,060,792, a catalyst for the oxidation of isobutyraldehyde was disclosed having Mo12P1.09V1.09Cu0.05Cs1.0.
In other patents such as Chinese Pat. No. 1047985A, U.S. Pat. Nos. 5,153,162 and 5,618,974, arsenic was added as a catalytic component. However, such a toxic component increases the risk of injury to humans and the environment during catalyst manufacturing and handling.
Although many catalysts for the oxidation of isobutyraldehyde to methacrylic acid have been disclosed, there is still a need in the art for alternative highly active, less toxic catalysts for that conversion, especially a catalyst capable of converting an aldehyde feedstock that may include isobutanal alone or a mixture of isobutanal and methacrolein.